Molecular Recognition of Fluoride Anion:  Benzene-Based Tripodal Imidazolium Receptor

Abstract

A benzene-based tripodal imidazolium receptor utilizing the strong (C-H)(+)...X(-) hydrogen bonding interaction between imidazolium moieties and halide anions is extensively investigated both theoretically and experimentally. Ab initio calculations predict that this receptor has a very high affinity for fluoride ion (F(-)). The association constant and free energy gain of the N-butyl receptor 2 for F(-) in acetonitrile were measured to be 2.1 x 10(5) M(-1) and -7.25 kcal/mol, respectively, showing that the receptor has a high affinity for F(-) in highly polar organic solvents.

Functionalized Ni@SiO2Core/Shell Magnetic Nanoparticles as a Chemosensor for Fluoride Ion

“…The fluorescence quenching effect can be explained as reverse photoinduced electron transfer (PET) when one ion is bound to the urea N-H protons behaving as a PET donor. [11][12][13][14]27 The fluorescence emission of the suspension of 1 in acetonitrile/water (1:1 v/v) gradually decreased with increasing additions of fluoride anion (Figures 2(c) and 2(d) To confirm the binding site of receptor 2 attached onto 1 with fluoride ion, solid 19 F NMR technique was applied to explore the interactions of 2 attached onto 1 with fluoride ion in the solid state. Before addition of fluoride ion to 1, no peak corresponding to fluoride appears, whereas peaks at −118 ppm appeared in the spectrum after addition of fluoride anion.…”

Understanding Clusters toward the Design of Functional Molecules and Nanomaterials

“…Various receptors showing either cation recognition [158][159][160][161][162] or anion recognition [163][164][165][166][167][168][169][170][171][172][173][174][175][176][177][178][179][180] have been synthesized and charcterized in the past decades. Despite these achievements, further research efforts are required to address the issues related to the selective recognition of anion/cation in real life samples for the environmental and biological use.…”

“…Thus, utilization of such ionic hydrogen bonding improves the binding affinity for the anion. Based on ab initio calculations, highly selective imidazolium-based anionophores have been designed [171][172][173][174][175][176][177][178][179][180] and synthesized. Imidazolium tripodal receptor 3 (Fig.…”

“…8) which has nitro substitution on the imidazolium moiety enhanced the strengh of the (C-H) þ ÁÁÁanion interaction as compared to the unsubstituted counterpart due to the enhanced dipole-charge interaction. 171,172 Fluorescent photoinduced electron transfer (PET) chemosensor for the recognition of pyrophosphate had also been designed and synthesized. [173][174][175][176][177] This fluorescent study with anions shows the pyrophosphate-induced maximal PET quenching effect.…”

What Anions Do Inside a Receptor's Cavity: A Trifurcate Anion Receptor Providing Both Electrostatic and Hydrogen‐Bonding Interactions

“…Selectivity depends both on energy terms (related to the intensity of the receptor-substrate interaction) and on geometrical factors (size and shape matching between receptor and substrate). Anions are prone to interact through either electrostatic or H-bond interactions, and thus the receptor must contain either positively charged groups (ammonium, [3] alkylammonium, [4] guanidinium, [5] pyridinium, [6] imidazolium, [7] coordinatively unsaturated metal ions) [8] or neutral hydrogen-bond donor groups (amides, [9] sulfonamides, [10] ureas, [11] pyrroles). [12] A variety of charged and neutral anion receptors have been synthesized during the last two decades.…”